It is known to place pacing leads in the area of the left ventricle via the coronary veins, e.g., for bi-ventricular pacing or resynchronization therapy. During such procedures, an electrical conductor (i.e., pacing lead) must be coupled to the left ventricle. In order to accomplish this in a minimally invasive fashion, the most common approach is by way of the coronary sinus and coronary venous system.
Such an approach can be difficult for a number of reasons. These include the inherent variability of venous anatomy, the multiplicity of turns that a device must take when tracking into the coronary sinus and/or its tributaries by way of subclavian or femoral vein approach, and the anatomical distortion that occurs secondary to diseases of the heart, as for example, heart failure or atrial fibrillation.
Furthermore, the design objectives of a lead system optimized for delivery often conflict with the design objectives of a system optimized to remain in stable position for long term pacing. For example, during delivery, a device is optimally lubricious and slides easily through the vasculature; however, once in place, the optimal device does not slide easily out of place, but remains in a stable position. As another example, during delivery, an optimal device has stiffness characteristics optimized to track around initial bends into the open chamber of the right atrium, into the lumen of the coronary sinus, and turn yet again into its tributaries. The optimal device during delivery should be pushable and hence have some degree of stiffness, whereas once in position the optimal device is generally flexible with high fatigue resistance. Furthermore, where the lead system specifically also includes a delivery component (e.g., sheath, guidewire, stylet, and the like) that is not left in the body, this component must be removed. Therefore, during introduction it is generally advantageous for his component to be stiffer and pushable, whereas during removal these properties may tend to dislodge the lead from it stable position.
Another problem associated with transvenous lead delivery is maintaining stable access into the coronary sinus and the coronary veins. Initial access of the coronary sinus may be difficult secondary to the presence of venous valve or tortuous or distorted anatomy. Once the coronary sinus has been accessed with a sheath or guidewire or other device, maintaining access is important and may be difficult during multiple exchanges of devices, for example a venography balloon catheter or pacing lead, or when attempting to move a pacing lead from one position to anther position.
Accordingly, apparatus and methods for delivering leads would be useful.